Project Summary IPUMS is a family of nine integrated databases that comprise the largest and most intensively-used data resource for research on population dynamics and health. This competing continuation proposal has two main goals. First, the project will provide the primary support for expanding, improving, and maintaining IPUMS-USA, which consists of microdata from decennial censuses and American Community Surveys. Second, the project will provide central coordination across the nine IPUMS databases, exploiting synergies and eliminating redundant work. Over the past five years, IPUMS has seen explosive growth in the number of researchers using the database, the amount of data they request, and the number of high-impact publications they produce. At the same time, however, there is unprecedented demand from researchers for expansion, improvement, and support of the infrastructure. This project will undertake four major activities to meet this demand: 1. Database expansion. The quantity of data in IPUMS-USA will expand dramatically over the coming five years to include harmonized datasets providing two billion records of individual-level information. 2. Data and metadata improvement. Improving the quality of IPUMS-USA data and metadata is a top priority. We plan (1) new variables on family forms, poverty, and health insurance; (2) new geographic measures; (3) streamlined categorical variables. 3. Data infrastructure improvement. The project will implement (1) multi-processor data access software that will improve data access speed and accommodate the rapidly growing demand for large-scale data; (2) a user-facing API to enable direct access by external applications; (3) sustainability planning for online data analysis; (4) new data access capabilities. 4. IPUMS coordination. The project will synchronize of technological development, user support and outreach, and long-run planning for preservation and sustainability planning across the nine IPUMS databases to avoid duplication of effort, increase the impact, and reduce the cost of IPUMS data infrastructure. IPUMS reduces costs for the population and health research community by minimizing redundant effort, simplifying data access, increasing the replicability of studies, and improving data reliability. The availability of large-scale integrated microdata has opened extraordinary new opportunities for fine-grained contextual analyses of population dynamics and health, resulting in transformational research across a diverse range of topics and disciplines.